| Polyacrylate emulsion has many merits,and it is widely adopted in varied fields.However,the heat resistance and poor hardness limits its application.Using inorganic nano-magnesium-aluminum hydrotalcite(MgAl-LDHs)to modify it can effectively solve these problems.However,the particle size of nano-MgAl-LDHs is small,and it has poor compatibility with polyacrylate.Therefore,improving the dispersion of MgAl-LDHs in polyacrylate is the key to preparing polyacrylate/nano-MgAl-LDHs composite emulsion.This work focuses on nano-MgAl-LDHs surface modification,polyacrylate/nano-MgAl-LDHs composite emulsion,composite emulsion polymerization mechanism,polymerization kinetics,composite emulsion-based and water-based fire-retardant coatings.The wet surface modification of nano-MgAl-LDHs powder by phosphate coupling agent(DN-27)was studied.The samples were characterized by infrared spectroscopy(FTIR),X-ray diffraction analysis(XRD),thermogravimetric analysis(TG),scanning electron microscope(SEM)and other test methods.The modification was studied meritlly grafted to the surface of MgAl-LDHs,and the agglomeration of nano-MgAl-LDHs is reduced after modification,and the dispersibility becomes better.The paper also explored the influence of the amount of phosphate coupling agent on the modification effect of MgAl-LDHs.The preparation of polyacrylate/nano MgAl-LDHs composite emulsion by the dropwise polymerization process was studied,and the optimal polymerization conditions were determined.The optimal conditions are 0.4%of initiator KPS,3%of compound emulsifier OP-10/SDS,2%of DN-27 modified MgAl-LDHs,and reaction temperature of 75°C.Using the well-determined conditions,the composite emulsion was prepared by in-situ emulsion polymerization process of batch method.The composite emulsion and latex film prepared by the two processes were characterized by FTIR,XRD,TG,and TEM.The analysis results show that the pure polyacrylate emulsion and composite emulsion synthesized by the two polymerization processes are successfully prepared.And the addition of MgAl-LDHs improves the heat resistance of the polyacrylate latex film.TEM analysis can also show that the nano-MgAl-LDHs in the composite emulsion prepared by the dropping method is dispersed into the latex particles.The kinetics of in-situ emulsion polymerization in the presence of nano-MgAl-LDHs was studied.By studying the influence of initiator dosage,emulsifier dosage,modified nano-MgAl-LDHs dosage and polymerization temperature on the polymerization rate,the apparent kinetic equation of polymerization reaction is obtained as Rp=K[I]1.62[E]0.33[MgAl-LDHs]-0.06.The apparent activation energy of the polymerization reaction system is 89.13k J·mol-1 calculated by the Arrhenius formula.And we are still studying in the dropwise emulsion polymerization process that the increase of the monomer drop rate Ra increases the reaction rate Rp.The preparation of polyacrylate emulsion and polyacrylate/nano-MgAl-LDHs composite emulsion to prepare water-based intumescent fireproof coatings was studied.The coating is tested by cone calorimeter and simulated large plate combustion method.The results show that the flame retardancy of water-based intumescent fireproof coatings prepared by polyacrylate/nano-MgAl-LDHs composite emulsion is higher than the flame retardancy of water-based intumescent fireproof coatings prepared by polyacrylate emulsion,and nano-MgAl-LDHs plays a key role in it. |
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